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Testing node->down requires the tree lock to be held.

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In decrement_reference only test node->down if the tree lock
is held.  As node->down is not always tested in
decrement_reference we need to test that it is non NULL in
cleanup_dead_nodes prior to removing the node from the rbt
tree.  Additionally it is not always possible to aquire the
node lock and reactivate a node when adding parent nodes.
Reactivate such nodes in cleanup_dead_nodes if required.
This commit is contained in:
Mark Andrews
2019-12-04 21:41:04 +11:00
committed by Ondřej Surý
parent 23e29b17db
commit 176b23b6cd
1 changed files with 22 additions and 5 deletions
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27
lib/dns/rbtdb.c
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@@ -1844,6 +1844,10 @@ cleanup_dead_nodes(dns_rbtdb_t *rbtdb, int bucketnum) {
/*
* Since we're holding a tree write lock, it should be
* impossible for this node to be referenced by others.
*
* decrement_reference may not have tested node->down, as
* the tree_lock was not held, before adding the node to
* deadnodes so we test it here.
*/
INSIST(isc_refcount_current(&node->references) == 0 &&
node->data == NULL);
@@ -1864,8 +1868,19 @@ cleanup_dead_nodes(dns_rbtdb_t *rbtdb, int bucketnum) {
attach((dns_db_t *)rbtdb, &db);
ev->ev_sender = db;
isc_task_send(rbtdb->task, &ev);
} else {
} else if (node->down == NULL && node->data == NULL) {
/*
* Not a interior node and not needing to be
* reactivated.
*/
delete_node(rbtdb, node);
} else if (node->data == NULL) {
/*
* A interior node without data. Leave linked to
* to be cleaned up when node->down becomes NULL.
*/
ISC_LIST_APPEND(rbtdb->deadnodes[bucketnum],
node, deadlink);
}
node = ISC_LIST_HEAD(rbtdb->deadnodes[bucketnum]);
count--;
@@ -1945,6 +1960,7 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
{
isc_result_t result;
bool write_locked;
bool locked = tlock != isc_rwlocktype_none;
rbtdb_nodelock_t *nodelock;
int bucket = node->locknum;
bool no_reference = true;
@@ -1952,12 +1968,12 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
nodelock = &rbtdb->node_locks[bucket];
#define KEEP_NODE(n, r) \
((n)->data != NULL || (n)->down != NULL || \
#define KEEP_NODE(n, r, l) \
((n)->data != NULL || ((l) && (n)->down != NULL) || \
(n) == (r)->origin_node || (n) == (r)->nsec3_origin_node)
/* Handle easy and typical case first. */
if (!node->dirty && KEEP_NODE(node, rbtdb)) {
if (!node->dirty && KEEP_NODE(node, rbtdb, locked)) {
if (isc_refcount_decrement(&node->references) == 1) {
refs = isc_refcount_decrement(&nodelock->references);
INSIST(refs > 0);
@@ -2024,8 +2040,9 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
refs = isc_refcount_decrement(&nodelock->references);
INSIST(refs > 0);
if (KEEP_NODE(node, rbtdb))
if (KEEP_NODE(node, rbtdb, locked || write_locked)) {
goto restore_locks;
}
#undef KEEP_NODE